Sixty Symbols was a website that produced videos about the many symbols of physics and astronomy (of course those are also the symbols of mathematics). The website is gone, but you can still find the videos.

Do you ever come across a Greek symbol in your reading and think, “now what does that stand for again?”  Professors and other experts at the University of Nottingham have made a series of YouTube videos that will (hopefully) jog your memory.

SixtySymbols is now archived on YouTube only.

Here’s ∞ (infinity) for your any level of math class after the first discussion of interval notation.

And j (for imaginary numbers, which is i in many U.S. math texts).

Or how about ω (angular velocity) for that Trig class you’re teaching?